Absorption refrigerator



m wwo J. LHTHGOW ET AL ABSORPTION REFRIGERATOR a sheets-sheet 2 Filed Jan. 17, 1942 J. LITHGOW ETAL ABSORPTION REFRIGERATOR WW u A 3 Sheets-Sheet 5 Filed Jan. 17, 1942 illl IHHH Illlllllll Julie refrigerators:

A familiar. and which householduse.

Patented Aug. 7, 1945' ammo 'l' OFFICE ABSORPTION REFRIGERATOR V John Llthgow, on Pllk, in, and Leslie 1:.

!Il, Cleveland, Ohio, assignors to buck and Co New York Jack Boe- Ili., a corporation of .1

Application January 17', 1942. Serial No. 427.166

4 claims. (Cl. e2-- 12o.s)

This application is a continuation-in-part of co-pending application Serial No. 214,441, flied 1938, now Patent 'No. 2,308,520.

Our invention relates in general to'the art of refrigeration, and in certain aspects. our invention is particularly applicable to absorption certain phase of our invention; however, are broadly applicable to refrigeration apparatus in general. i

An object of our invention is to provide as improved evaporator, certain features of which are especially applicable to an absorption type of thisspecification and illustrationg certain preferred embodiments of our invention,

Fig. 1 is a diagrammatic representation. of an intermittant' cycle absorption refrigerating sysembodying ourinvention: Fig. 2 is a side elevatlonal view partly in section through an improved evaporator embodying our invention;

refrigerator while other features are broadly applicable to frigeratora.

I Another object is to provide an evaporator taper in cross sectional diamof the rethis as well as other types of resurfaces engageable' .with said coil. are formed with a similar taper, so that'a wedging fit is obtained between the brine tank and said coils, thus providing close engagement between said elements and emcient heat conduction as well as making more convenient tion of the brine tank movaltherefrom. 1 1

Another object is to provide an evaporator in the applicacausing disturbance.

sou another oblectiis to provide in generalnro d mc r. compared with the,

economy and simplicity as prior art with which we are Fig. 3 is a perspective view of an improved I evaporator coil forming-apart of the evaporator shown in Fig. 2, certain parts being broken away to show the construction more clearly; I

Fig. us an elevational view partly in section.

" of our improved evaporator construction and to the coils and its reis especially applicable to 1 leading to a showing the means for mounting the same, said view being taken from the rear of the -evaporator or from the left of Fig. 2;

Fig. 5 is a perspective. view in more'or less diagrammatic form. of an evaporator which is another embodiment of our invention; and

Fig. 6 is a detailed fragmentary sectional view taken substantially along the line 6-6 of Fig. 5.

Referring first to Fig. 1, the numeral ill repfunctioning also as an absorber, and adapted to contain a solution of a refrigerant gas (pref erab1y ammonia) in a liquid (preferably water). A U-shaped conduit l2. which may be referred was a steam tube. connects 'the still ill with a main liquid trap II, the conduit i2 preferably extending below the liquid in the .trap, said level being indicated by the line A- -A. An overflow pipe I5 carries liquid from the trap l3 back to the bottom of the stllllll.

A conduit l8 extends from the upper portion of the trap- II to form a dehydrator, said conduit It being preferably of generally uformation and the downwardly extending legs of the U having heat dissipating fins l8 thereon. The dehydrator i6 communicates; with an enlarged receptacle l9 forming a secondary trap, the latter having a return pipe 20 communicating with the main tra'p II.

A conduit 22 extends from the upper portion of the secondary trap-l9, communicating with a' conduit 24 which leads to an evaporator 20. a smaller tube 2! cutting into the pipe "and condenser 2| which may be inthe form of a coil or loop in vertically inclined flights. .The tube 25 extends into a sump 28 in the condenser receiver 21. v t

The conduit 24 also serves to return refriger'ant gas to the still-absorber, said conduit 24 preferably communicating with a loop or coil 7 Q5 which may also, be provided with heat dissipating fins, said loop- I! being connected to the bottom of the still-absorber at longitudinally spaced points and preferably being arranged in nights which are staggered vertically and horizontally. similarly to the condenser coils 20.

As is well known, it is highly essential in absorption refrigerators that any water which trap and dehydrator and be carried over to the evaporator be withdrawn from said evaporator at the heating period of the cycle, inasmuch as accumulations of such liquid would seriously detract from the efficiency of the evaporator. We have provided an improved drain of greatly increased efficiency which is simple in construction and certain in operation. It is highly important that th drain does not function during the refrigerating period. as such action would withdraw liquid refrigerant. reducing the length of the refrigerating period and detracting from the efliciency of the apparatus. We have provided a drain which insures against such malfunctioning.

Our improved drain comprises a tube 3! having its inlet in a sump 3l-in the evaporator adiacent the bottom thereof and communicating with the upper portion of a receptacle 3! which may be an enlarged cylindrical member as shown. Liquid is withdrawn from the bottom of the receptacle 39 by means of a conduit having a down leg 40 and an up leg 42, said up legcommunicating with the bottom of the main trap I3 below the liquid level thereof. i

In the operation of the device just described, at the beginning of the heating period of the cycle. heat is applied to the bottom of the still I! by any suitable means (not shown). said still at this time containing a strong solution of the refrigerant in its absorbent liquid (water), and the refrigerant together with some of the liquid in the form of vapor is driven off through the conduit i2, part of the liquid being separated out in the trap l3 and returned via the overflow pipe IS to the still ID. The refrigerant gas and the remaining water vapor then passes by way of conduit ii to the dehydrator l0, additional liquid settling out in the secondary trap is and being returned by the overflow pipe 20 to the main trap is. The refrigerant gas which is now nearly in anhydrous condition passes through the tubes 22, 24 and 25, to the condenser coils 20, collecting as a liquid in receiver 21.

At the end of the heating cycle, pressure in the still l subsides and the liquid refrigerant reverses its direction, traveling upwardly from the condenser receiver 21 to the evaporator receiver 30, flowing into the evaporator; coils 32, where it performs its refrigerating function, and then returns to the still, now functioning as an absorber, via the conduit 24.

The operation of the drain is described in full assopvo In accordance with our invention, the coil 10 encased in a material formed. molded or thereon which is of such nature that it will tend to disintegrate or corrode as does steel or set up a corrosive action in the brine tank. We

employ in our preferred embodiment a die castsheathing bracket II which is preferably ofalu-' lightness of weight and inability to set up any substantial corrosive action with the metal of the brine tank. Various molded plastics may be found suitable. The die casting or other material applied to the coils may be formed in any suitable cross sectional form, either square as shown, round, etc., and may be conveniently applied to the convolutions of the coils after they have been bent.

Although we have shown this feature of our invention as applied to a series coil evaporator, it will also be found applicable to a parallel or series-parallel type of coil.

detail in our co-pending application Serial No.

214,441, now Patent N0. 2,038,520.

Evaporaton-Sd far as is known, it is necessary that evaporator coils in a system employing ammonia under high pressure as the refrigerant be formed of ferrous metal, usually steel, and such coils as well as the brine tank mounted thereon are highly subject to rusting or corrosion. This oxidation is greatly enhanced by reason of the ionization or galvanic action set by upcontact of the coil with the metal of the brine tank which must be in close proximity to the coil, since the brine tank is usually formedl of a dissimilar metal such as aluminum.

Itwillbenotedfromaninspectionofl igaii and 3 that the die casting 1i increases in cross sectional diameter from front to rear of the cabinet or brine tank. We have found this arrangement to be highly advantageous in that it permits the brine tank to be slidably lodged upon the coil or removed therefrom, and it also i *sures an improved fit or contact between the external surfaces of the brine tank and the coil. When the brine tank is to be applied, it is shoved from front to rear onto the coil, assuming a wedging fit on the coil which is quite secure, and by reason of the improved contact more efllcient heat conduction is provided. The surfaces of the brine tank. which may be of the form featured in UrB. Patent No. 2,313,080, which contact the casting brackets 1| should be tapered to conform to the tapered casting. Any inaccuracy in forming the brine tank or resulting from warping thereof,

after its fabrication is easily compensated for by the taper, any play which otherwise might exist being taken up by the wedging fit.

Formed integrally with the die casting 1| at the rear of each convolution thereof are oppositely extending perforated ears 12 whereby the coils may be secured'as by screws 13 or other suitable means to the rear of the refrigerator casing indicated generally by the numeral 14.

,In the preferred embodiment shown, a plate 1!- secured to the back wall 10 of the cabinet as by screws 11 provides a support to which the ears 12 are secured, suitable insulating washers 1| being interpowd between the ears 12 and the back plate. The back plate 15, as seen best in Fig. 2, is stamped inwardly to provide clearance space for the screws and nuts. This type of support is strong and rigid and places all the load on the back wall of the case 14.

In the evaporator shown in Figs. 2 and 4. numeral 80 represents the evaporator receiver from which refrigerant liquid flows through tube 8| through a sump 83 thence to the bottom coil of the evaporator from which it flows in series through the other coils, the various convolutions of the evaporator coil being connected by tubular portions 04 which are welded to the coils 1|. The uppermost coil convolution is connected to or integral with the receiver II by pipe 85, serving as a gas return, and a drain tube it extends into the sur'np ll below the level of the lowermost coil, as at Figs. 5 and 6 show another form of improved evaporator, which is applicable to an intermittent cycle absorption refrigerator. The numeral 90 represents an evaporator receiver having a liquid supply tube 900. and a, gas return 90b, from which refrigerant is withdrawn by means of a supply leg 9| having its inlet in the bottom of the receiver 90. The liquid supply leg 9| connects with an up leg 92, an enlarged sump 93 being provided at the bottom thereof, a, drain tube 95 extending upwardly from the sump. The drain tube of course may, if desired, extend through the down leg 9| for convenience. A gas return conduit 96 having its opening in the upper portion of the receiver 90 extends downwardly to a, level somewhat higher than the sump 93, and connecting the manifold leg 92 with the gas return conduit 96 is a plurality of parallel coils 91. The evaporator coils 91 are preferably U- shaped and extend well into the legs 92 and 96 as show best in Fig. 6, the ends thereof being closed as by the use of plugs 98 and provided with openings 99 in the upper portion thereof within the legs 92 and 96 respectively.

Before describing the action of this improved design of evaporator, it will be interesting to consider some of the problems encountered in the prior art. At the beginning of the heating period of the cycle in an intermittent cycle absorption refrigerator, the liquor in the evaporator is usually of a concentration of about 50% as a result of weakening during evaporation. This diluted liquor is drained out at the beginning of the heating period,-thus permitting condensation of the refrigerant gas in the empty coils and resulting in heating the brine tank and decreasing effective holdover capacity. In devices of the prior art, gas is formed in the evaporator coils, due to the effect of the brine tank being warmer than the evaporator coils 91, and thus volatilizing gas therein, which gas may have a tendency to build up large gas pockets which from time to time are forced violently out of the evaporator coils, causing violent surging or gas lock hammering which might result in undesirable draining of refrigerant and thus seriously detracting from the efllciency of its operation.

Our improved evaporator, as shown in Figs. and 6, has been especially designed to avoid such conditions. Any gas which may be formed in the coils 91 will promptly flow out of these tubes in the direction shown by the arrows to the gas return conduit or gas riser 96, thence flowing back to the receiver 90. If desired, the coils 91 may rise slightly from their ends in the leg 92 to their ends in the conduit 96, in order to facilitate gas movement in the direction shown, although such slanting is not absolutely required. Thus, gas pocketing in the coils 91 cannot occur.

By plugging the ends of the evaporator coils 91 in the manner shown in Fig. 5 and providing their openings 99 in the top of said coils, it is impossible for the coils to be emptied when the coils 91 and it will be drained.

assured for proper operation during the heating period.

At the beginning of the refrigerating period, fresh refrigerant enters the coils from the condenser, flushing out the liquid residue therefrom, so that each refrigerating period begins with a fresh supply of refrigerant in the evaporator.

Various changes coming within'the spirit of our invention may suggest themselves to those skilled in the art, and hence we do not wish to be restricted to the specific forms shown or uses mentioned except to the extent indicated in the appended claims, which are to be interpreted as broadly as the state of the art will permit.

We claim:

1. In an intermittent absorption refrigerator, an evaporator comprising a receiver. a liquid supply header, 9, gas return header, and a plurality of tubes connecting said headers, said tubes communicating with said headers only in the upper portion of said tubes, whereby liquid may not be substantially drawn out of said tubes by the draining action, and drain means associated with one of said headers.

2. Adevice as claimed in claim 1, wherein said evaporator tubes are inclined slightly upwardly from the liquid header end to the gas header end in orderv to facilitate elimination of gas formed in said tubes without permitting liquid substantially to flow out of said tubes.

3. In an intermittent absorption refrigerator, an evaporator comprising a liquid header and a gas return header, said liquid header having a down leg and an up leg closed at the end thereof. and a plurality of evaporator tubes connected between the gas return header and said up leg,

said liquid header having a sump therein, and

a drain tube communicating with said sump.

4. In a refrigerator, an evaporator unit including a tubular conduit disposed in a substantially horizontal plane with a rigid enclosing sheath molded around said conduit and including a vertically extending flange through which the conduit emerges, together with fastening means securing said flange to a vertical wall of the refrigerator, whereby said evaporator unit projects from such wall in position to support a load and said sheath is adapted to substantially prevent the'imposition of such load upon the conduit.

JOHN LITHGOW. LESLIE K. JACKSON.

will also flow over 

